The present invention relates to a sealed joint structure for joining mechanical or structural parts by interposing therebetween sealant and more specifically to an improvement in sealed joining of two parts each having joining surfaces meeting at right angles and requiring to be sealed at the same time.
An automotive engine has a plurality of cam brackets (also called bearing caps) fixedly attached to an upper joining surface of a cylinder head so as to support therebetween a camshaft as is for example disclosed in Japanese Patent provisional Publication No. 10-47019.
In some automotive engine, a front cover is disposed at the front side of a cylinder head and a cam bracket and fixedly attached thereto.
FIGS. 8 to 10 show a structure for joining a cam bracket 3 to a cylinder head 2 and a front cover 4. With such a structure, sealant is applied to the upper joining surface S1 of the cylinder head 2, and then the cam bracket 3 and the cylinder head 2 are positioned relative to each other by means of a depression 9 of the cam bracket 3 and a projection 8 of the cylinder head 2 and joined together, as shown in FIG. 9, with the sealant being disposed therebetween (actually, two pairs of projections 8 and depressions 9 are provided though only one pair is shown).
Then, sealant is applied to a joining surface S2 of the front cover 4, and thereafter the front cover 4 is joined to the cylinder head 2 and the cam bracket 3, as shown in FIG. 10, by interposing therebetween the sealant.
Sealing of the cam bracket 3 with respect to the joining surfaces S1 and S2 is necessitated for preventing a lubricant for lubrication of a bearing portion of the cam bracket 3 from leaking or oozing out from the cam bracket 3.
A problem of the above described joining structure is that in case the cam bracket 3 is removed for removal of a camshaft after they are once assembled, reinstallation of the cam bracket 3 requires removal of the front cover 4 due to the necessity of carrying out the sealing process steps in the same order as that at the first assemblage.
This is for the following reason. In order to reinstall the cam bracket 3, without removal of the front cover 4 as shown in FIG. 11, after application of sealant to the joining surfaces S1 and S2 of the cylinder head 2 and the front cover 4, the cam bracket 3 must be moved downward while being held in contact with the joining surface S2 of the front cover 4, thus allowing the sealant on the joining surface S2 to be scraped off and therefore causing a defective seal.
Accordingly, for attaining a desired seal between the front cover 4 and the cam bracket 3 at the time of reinstallation of the cam bracket 3, removal of the front cover 4 is inevitable, thus making the working time necessary for the reinstallation longer.
It is accordingly an object of the present invention to provide a novel and improved structure for joining a pair of first and second parts together which can attain a good simultaneous seal between two pair of joining surfaces each meeting at right angles, notwithstanding a pair of positioning projections are provided to one of the joining surfaces for positioning the first and second parts relative to each other.
It is a further object of the present invention to provide a method of joining the above described pair of parts which can attain a good simultaneous sealing between two pairs of joining surfaces each meeting at right angles.
To accomplish the above object, the present invention provides a novel and improved structure for joining a first part having a pair of first and second internal joining surfaces meeting at right angles and a second part having a pair of first and second external joining surfaces meeting at right angles in such a manner that the first and second internal joining surfaces are respectively joined with the first and second external joining surfaces by interposing therebetween sealant for thereby providing a seal between a pair of the first internal joining surface and the first external joining surface and between a pair of the second internal joining surface and the second external joining surface, the structure comprising a pair of depressions provided to the first external joining surface, a pair of projections provided to the first internal joining surface at locations corresponding to the depressions for insertion into the depressions and thereby positioning the second part relative to the first part, and a pair of slanted guide grooves provided to inner circumferential surfaces of the depressions for guiding the insertion of the projections into the depressions, respectively, each of the guide grooves being disposed between each of the depressions and an edge at which the first and second external joining surfaces meet, and formed so as to expand each of the depressions increasingly toward an open end of each of the depressions.
It is a further object of the present invention to provide a novel and improved method of joining a first part having a pair of first and second internal joining surfaces meeting at right angles and a second part having a pair of first and second external joining surfaces meeting at right angles in such a manner that the first and second internal joining surfaces are respectively joined with the first and second external joining surfaces by interposing therebetween sealant for thereby providing a seal between a pair of the first internal joining surface and the first external joining surface and between a pair of the second internal joining surface and the second external joining surface, the second part having an edge at which the first and second external joining surface meet, wherein a pair of projections are provided to the first internal joining surface and a pair of depressions are provided to the first external joining surface at locations corresponding to the projections and fittingly engageable with the projections for positioning the second part relative to the first part, the method comprising providing each of the depressions with such a slanted guide groove that is located between each of the depressions and the edge of the second part and formed so as to expand each of the depressions toward an open ends of each of the depressions, and guiding insertion of the projections into the depression by the guide grooves such that the first and second external joining surfaces are respectively brought into contact with the first and second internal joining surfaces nearly simultaneously.